In order to protect metallic portions of a substrate for electronic devices and easily bond the substrate to other electronic devices, selected portions of the metallic portions have heretofore been partially plated. There are various types of plating methods, and typical plating methods are wet electroplating and electroless plating.
Wet electroplating is conducted by covering or masking portions other than selected portions in advance, and partially plating the selected portions. Wet electroplating, therefore, has the following problems: application to fine portions on a substrate for electronic devices on which semiconductor products are to be mounted is not suitable; and control of the plating amount is difficult.
Moreover, wet plating has another problem in that plating cannot be performed unless the article to be plated is made electrically conductive. Furthermore, since wet electroplating uses large amounts of solutions such as a plating solution and a cleaning solution, it requires a large scale treating facility, which tends to cause an environmental problem.
On the other hand, since the electroless plating is conducted with chemicals such as an acid or an alkali without utilizing electrolytic reactions, there arises the problem that the metals which can be used for plating are restricted.
Furthermore, in order to plate selected portions alone, the selected portions must be subjected to surface treatment; therefore, electroless plating has the problem that it requires many elaborate procedures. Still furthermore, electroless plating has disadvantages in that it is difficult to form a thick plated layer and that the plating amount varies.